Unlike dual-shape-memory polymers which have been summarized in the literature and which can accomplish the network formation by both physical interactions as well as by covalent bonds, triple-shape-memory polymers have thus far been described only as networks based on covalent bonds [Bellin, I. et al., Polymer triple-shape materials, PNAS (2006), 103(48), p. 18043-18047]. Such triple-shape-memory polymer networks consist of at least one type of covalent cross-linking sites and at least two types of switching segments. In analogy to a dual-shape-memory polymer networks, triple-shape-memory polymer networks may contain, among others, segments of poly(ε-caprolactone), polyethers, polyether urethanes, polyimides, polyether imides, poly(meth)acrylate, polyurethane, polyvinyl compounds, polystyrenes, polyoxymethylene or poly(para-dioxanone). Introduction of hydrolysable groups, such as diglycolide, dilactide, polyanhydrides or polyorthoesters can produce biodegradable triple-shape-memory polymers [Lendlein, A. & Langer, R.: Biodegradable, elastic shape-memory polymers for potential biomedical applications. Science, 2002. 296 (5573): p. 1673-1676, Lendlein, A. & Kelch, S.: Degradable, Multifunctional Polymer Biomaterials with Shape-memory. Materials Science Forum, 2005. 492-493: p. 219-224].
Polymer networks, which enable the triple-shape-memory effect, can be configured as AB-networks, where both chain segments contribute to the elasticity or as side chain networks, where the segments between the cross-linking sites predominantly contribute to the elasticity. The first may be realized, for example, by the polymerization of poly(ε-caprolactone)dimethacrylate with cyclohexylmethacrylate (MACL). A side chain network can be realized by the polymerization of poly(ε-caprolactone)dimethacrylate with polyethylene glycol monomethylether methacrylate (CLEG). Both network architectures are graphically illustrated in FIG. 1; (1) indicates here PCHMA segments; (2) PCL segments; (3) PEG side chains; and (4) cross-linking sites.
For programming purposes, segment of the test samples must be brought into a temporary form. The following exemplary methods may be used for programming:                Temporarily increasing the temperature above the switching temperature(s) Tswitch with subsequent deformation        Temporarily introducing plasticizers, so that the ambient temperature is above Tswitch, with a subsequent deformation and removal of the plasticizer.        
Programming of a different segments of the component must here be performed separately for each segment of the component, whereby care has to be taken that the programming of a particular segment does not cancel the programming of another segment. The programming is done in dependence of the switching temperature. This means that in practice the segment with the highest Tswitch is programmed first, whereafter the temperature is sequentially lowered, followed by programming of additional segments. In addition, different programming methods can be used for individual segments.
For retrieving the two shape changes of the component, the component must be moved into the heat-transmitting medium, wherein the temperature of the medium is successively increased, until the first shape change occurs. The additional shape change of the component occurs only when the temperature of the medium is increased further.
The principle of the triple-shape-memory polymers (or triple-shape polymers) has already been described in detail. Known segments are here based, on one hand, on the combination of segments made of polyethylene glycol (PEG) and poly(ε-caprolactone) (PCL) and, on the other hand, on the combination of PCL and cyclohexyl methacrylate (CHMA). The switching temperatures for using the triple-shape-memory effect are in the first case at 40 and 70° C. and in the second case at 70 and 130° C. In both cases, the shape change of components made from different material classes can only be stimulated through heat conduction of the air and hence takes a long time (40 to 80 minutes). Water is a very good heat transfer medium, but is not available for either polymer system, because it causes in PEG/PCL system swelling of the network due to the hydrophilic characteristic of PEG. Crystalline PEG regions may also swell, thereby negating the physical cross-linking required for the triple-shape-memory effect. In the PCL/CHMA system, water cannot be heated to the required switching temperature of 130° C. under normal pressure. Several applications, for example in the medical field, require complex shape changes, in particular those which includes a sequential order of the shapes A→B→C, sometimes within very short time intervals. It may for example be necessary to reshape a “round” tube into an “oval” tube and then back into a “round” tube. Until now, none of the aforedescribed triple-shape-memory polymers can produce this deformation in an aqueous environment. The shape changes attainable so far are limited by the programmable shapes, a movement of the test sample is so far only feasible to the extent to which this shape change has previously been programmed. In particular, two-dimensional or three-dimensional movements are severely limited. An additional disadvantage of the conventional systems is their low elasticity, in particular below the switching temperature.
The conventional systems have therefore the following disadvantages:                Until now, the use of the one-way shape-memory effect allows only a one-time change of a shape by thermal stimulation. The change of the stimulation conditions, for example an additional increase of the temperature, has no effect on to the shape of a component, if Tperm is not exceeded, which would cause melting of the component with thermoplastics.        With the introduction of the triple-shape-memory polymers, it becomes possible to realize all together three different shapes of the component. The successive stimulation of the individual shapes is attained by a temperature increase after suitable programming of the component. However, programming of known triple-shape-memory polymers is very demanding.        The material should provide high elasticity, i.e., high elongation at break, in particular greater than 400% at room temperature. However, known triple-shape-memory polymers have significantly lower elasticity.        Known triple-shape-memory polymers are sensitive to water, so that water is eliminated as a particularly effective heat transfer medium. The swelling properties and switching temperatures do not allow a shape change in water.        
The aforementioned problems have so far not been solved, although the recently introduced concept of triple-shape-memory polymers has opened the possibility for sequential control of the thermally induced shape-memory effect. Neither a one-step programming of the triple-shape-memory effect at room temperature, nor a high elongation at break>400%, nor a variation of the trigger temperature through selection of the programming temperature have been realized to date with triple-shape-memory materials. It has also not been possible to date to make the triple-shape-memory effect reversible, renewed programming has so far been required after each shape recovery.
It is therefore an object of the invention to solve or at least alleviate one or more of the aforementioned problems.